18 April, 2017

Your taxes are due today.

Major links

• Network Administration in 1995!
  • YP has largely been replaced by Kerberos, LDAP and Active Directory
  • Fibre Channel is a bit like FDDI
  • ATM was used at UNC Asheville
  • Virtual machines use virtual networks
  • NAT is everywhere
  • Cisco is everywhere (except your house)
  • IP6 will replace IP4 (maybe)
• Chapters 9 & 10 (networking) of How Linux Works

Follow along with How Linux Works

Connect to How Linux Works and following along. Use your workstation and Pi and notebook.

Section 9.2 — Network Layer

You need to know the layers; but add the MAC layer.

What is the MAC layer address of your device? Use ifconfig.

Section 9.3 — Internet Layer

What is the MAC and network layer addresses of your device? Use the ifconfig and ip commands.

Everyone uses CIDR but evidently the Cisco exams still mention class A, B and C networks. Look at section 9.3.2 and think about using your CSCI 255 skills to determine if an IP host is on your LAN.

• 152.18.0.0/16 is the UNC Asheville network
• 152.18.69.0/24 is the UNC Asheville CSCI network
• Many (maybe most) computers are located on private networks.
• A manually configured /etc/NetworkManager/system-connections/Wired connection 

Section 9.4 — Routes

• route -n
• ip route
• netstat -r

The main campus routers have routing tables with bazillions of entries.

Section 9.5 — Tools

• ping
• traceroute
• host
• arp
• nslookup
• dig

Section 9.6 — Physical layer

• arp

Section 9.7 — Kernel networking

• ifconfig but read the details

Section 9.8–9.11 — How the network is managed

With Ubuntu, it’s NetworkManager. With Raspbian, it’s dhcpcd. Both use wpa_supplicant to handle wireless connections.

Section 9.12 — Resolving hostnames

• /etc/nsswitch.conf
• /etc/hosts
• /etc/resolv.conf
• UNCA CS name server files

Simulate a FQDN to IP lookup using dig,but remember that your computer caches its host lookups.

Section 9.13 —

There’s no place like home.

Section 9.14 — Transport layer

• netstat -ntl
• netstat -nt
• netstat -t
• netstat -an
• sudo lsof -i :auth

You can start and accept connections from the command line.

• nc -l 3333
• nc -k -l 3333
• nc hostname 3333
• printf "GET /sysadmin HTTP/1.0\r\n\r\n" | nc www.cs.unca.edu 80
• printf "GET /sysadmin/ HTTP/1.0\r\n\r\n" | nc www.cs.unca.edu 80

Section 9.16 — DHCP

Look at the computer science DHCP configuration file.

Section 9.19 — Network Address Translation

Look at a login session to a home router.